Steve Hilton is among the political figures that Tim Collins allegedly claimed he could gain access to. Photograph: Peter Macdiarmid/Getty Images

The Labour party has raised fresh questions over government links to lobbyists after secret tapes suggested senior figures at a prestigious lobbying firm could offer repressive regimes privileged access to Downing Street.

The Bureau of Investigative Journalism said that Tim Collins, a senior director at Bell Pottinger and former Tory MP, had claimed he could gain access to Steve Hilton, David Cameron's chief strategist; Ed Llewellyn, Cameron's chief of staff and even foreign secretary William Hague.

Collins's claim came after a member of the bureau went to Bell Pottinger, as well as a number of other lobbying firms, posing as a member of the Uzbek government wanting to clean up the regime's image in the west.

The Labour party said: "These are very serious allegations involving a former member of the Conservative frontbench as well as some of David Cameron's closest confidants inside Downing Street and his cheerleaders in the media."

The allegations against Bell Pottinger appear in the Independent but the Guardian has not had access to any of the secret tapes.

The shadow Cabinet Office minister, Jon Trickett, said: "We have been calling on the government to implement a statutory register of lobbyists. We need reform to ensure that there is no question of the rich and powerful buying access to the prime minister and his advisers."

A Downing Street spokesman said: "Bell Pottinger nor any other lobbying firm has any say or influence over government policy."

But, in the secret recordings, the lobbyists claim they have used their access to No 10 to get David Cameron to speak to the Chinese prime minister on behalf of one of their business clients within 24 hours of asking him to do so.

They also assert they could manipulate Google results to "drown" out negative coverage of human rights violations and child labour, and add that Bell Pottinger has a team which "sorts" negative Wikipedia coverage of clients. They also claim it was possible to use MPs known to be critical of investigative programmes to attack their reporting for minor errors.

Collins, managing director of Bell Pottinger Public Affairs, told the reporters he used to be Llewellyn's boss in Conservative Central Office, and had worked with Cameron and chancellor George Osborne in the Conservative research department.

"I've been working with people like Steve Hilton, David Cameron, George Osborne for 20 years-plus. There is not a problem getting the messages through," he said.

In the tapes, Collins's colleague David Wilson said the firm was the "most powerful public affairs business in the country" and it could help organise a meeting between Cameron and the Uzbek president – despite protocol dictating that such meetings are organised by ambassadors.

Collins later clarified that such a meeting might be an "end point" to aim for, once the country was seen to be genuinely improving its human rights record.

Collins also recommended a meeting with Daniel Finkelstein, chief leader writer at the Times – who he said was very close to Cameron. "He will sit down and have lunch with just about anybody," he said. "That doesn't mean he's going to agree with them, but occasionally something out of that lunch will get dropped into a future column."

Discussing techniques for managing reputations online, Wilson mentioned a team that could "sort" Wikipedia.

"We've got all sorts of dark arts," added Collins. "I told him [David Wilson] he couldn't put them in the written presentation because it's embarrassing if it gets out."

A presentation shown during the meeting said it could "create and maintain third-party blogs" – blogs that appeared to be independent. These would contain positive content and popular key words that would rank highly in Google searches.

"There are a lot of people in Parliament who can't stand Channel 4 and can't stand Dispatches," Collins said.

"So if there are any inaccuracies, even if they're fairly minor, you can work with some people who have a track record of not liking Channel 4, wanting to score points against Channel 4 [who will say:] 'Here is another instance of Channel 4 over-reaching themselves and putting out stuff they haven't properly checked'."